Change teleport to have varying channel times
If you are teleporting from base to a lane tower, since you have direct line of sight (clear and unobstructed path from fountain to a friendly lane tower) you should have a short channel time. Where as teleporting in between lanes, say from friendly top outer to enemy bot inner, the teleport should take longer.
Or longer distances = longer channels to an extent. For example half map (roughly spawn to outer turret) = 3.5 seconds, where cross map (say top lane outer turret to bot lane outer turret) = 4.5 seconds, and anywhere in between is set somewhere inbetween.